Anisole nitration during gamma-irradiation of aqueous nitrite and nitrate solutions: free radical versus ionic mechanisms

2010 ◽  
Vol 7 (2) ◽  
pp. 183 ◽  
Author(s):  
Gracy Elias ◽  
Bruce J. Mincher ◽  
Stephen P. Mezyk ◽  
Thomas D. Cullen ◽  
Leigh R. Martin
Keyword(s):  
Free Radical ◽  
Water Treatment ◽  
Condensed Phase ◽  
Aromatic Compounds ◽  
Nitrous Acid ◽  
Radical Reactions ◽  
Electrophilic Aromatic Substitution ◽  
Aromatic Substitution ◽  
Beam Irradiation ◽  
Free Radical Reactions

Environmental context. The nitration of aromatic compounds is an important source of toxic, carcinogenic, and mutagenic species in the atmosphere. Gas phase nitration typically occurs by free radical reactions. Condensed-phase free radical reactions may also be relevant in fog and cloud water in polluted areas, in urban aerosols with low pH, in water treatment using advanced oxidation processes such as e-beam irradiation, and in nuclear waste treatment applications. This paper discusses research towards an improved understanding of nitration of aromatic compounds in the condensed phase under conditions conducive to free radical formation. Abstract. In the irradiated, acidic condensed phase, radiation-enhanced nitrous acid-catalysed, nitrosonium ion, electrophilic aromatic substitution followed by oxidation reactions dominated over radical addition reactions for anisole. This ionic mechanism would predominate in urban atmospheric aerosols and nuclear fuel dissolutions. Irradiated neutral nitrate anisole solutions were dominated by mixed nitrosonium/nitronium ion electrophilic aromatic substitution reactions, but with lower product yields. Solutions such as these might be encountered in water treatment by e-beam irradiation. Irradiation of neutral nitrite anisole solutions resulted in a statistical substitution pattern for nitroanisole products, suggesting non-electrophilic free radical reactions involving the •NO2 radical. Although often proposed as an atmospheric nitrating agent, NO2 radical is unlikely to have an important effect in the acidic condensed phase in the presence of more reactive, competing species such as nitrous acid.

Recent advances in structure and reactivity of dissolved organic matter in natural waters

2008 ◽  
Vol 8 (6) ◽  
pp. 615-623 ◽  
Author(s):  
William J. Cooper ◽  
Weihua Song ◽  
Michael Gonsior ◽  
Daina Kalnina ◽  
Barrie M. Peake ◽  
...  
Keyword(s):  
Organic Matter ◽  
Free Radical ◽  
Water Treatment ◽  
Dissolved Organic Matter ◽  
Carbon Cycling ◽  
Natural Waters ◽  
Anthropogenic Sources ◽  
Radical Reactions ◽  
Detailed Knowledge ◽  
Free Radical Reactions

The goal of our research is to better understand the structure and reactivity of natural dissolved organic matter (DOM) in aquatic environments. A more detailed knowledge of these DOM characteristics would lead to a better understanding of carbon cycling in natural waters and processes associated with water treatment using free radical chemistry. Our specific interest in DOM in natural waters is several-fold: 1) the photochemical formation of reactive oxygen species, 2) photobleaching of the DOM in coastal oceans, and 3) using chromophoric DOM (CDOM) as a tracer of water masses and in carbon cycling. Our interest in water treatment is that DOM is the major sink of hydroxyl radicals employed in advanced oxidation processes for the destruction of pollutants and thus adversely affects the efficiency of the process. We are using the techniques of radiation chemistry to explore the fundamental free radical and redox chemistry of DOM. We have initiated a study of the free radical reactions of DOM using isolated fractions of Suwannee River fulvic and humic acids and isolates from various anthropogenic sources. We are also investigating the use of model compounds in an attempt to understand the free radical transients formed from DOM either as a result of free radical reactions or photochemical reactions.

Sterically hindered aromatic compounds. VIII. Comparative photochemistry of 2,4,6-tri-tert-butyl- and 2,5-tert-butylnitrosobenzenes

1978 ◽  
Vol 56 (20) ◽  
pp. 2665-2672 ◽  
Author(s):  
L. Ross C. Barclay ◽  
Derek Leigh Carson ◽  
Jean A. Gray ◽  
Michael Grossman ◽  
Prabhaker G. Khazanie ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Free Radical ◽  
Hydrogen Atom ◽  
Aromatic Compounds ◽  
Complex Mixture ◽  
Radical Reactions ◽  
Product Analysis ◽  
Free Radical Reactions ◽  
Tert Butyl ◽  
Conformational Effects

Ultraviolet irradiation of hydrocarbon solutions of 2,4,6-tri-tert-butylnitrosobenzene (1) formed [Formula: see text] The initial products were 2-methyl-1-nitroso-2-(3,5-di-tert-butyl)-phenylpropane (Ar—C(CH3)2CH2NO)2 (3) and a mixed dimer (4). Secondary and minor photoproducts isolated included 2-methyl-2-(3,5-di-tert-butyl)phenylpropanal oxime (5), 2-methyl-2-(3,5-di-tert-butyl)phenylpropanal (6) derived from 5, and 1,3,5-tri-tert-butylbenzene (7). The initial products are explained by formation of a tri-tert-butylphenyl radical (15), rearrangement of a hydrogen atom from an orthotert-butyl to the ring in 15, and rapid recombination of the neophyl radical with nitric oxide. Photolysis of 2,5-di-tert-butylnitrosobenzene (2) initially gave [Formula: see text] (10). Product analysis indicated a comparatively complex mixture including 1,4-di-tert-butylbenzene (11), 2,5-di-tert-butylphenol (12), and 2,5-di-tert-butylanilino-p-(2,5-di-tert-butyl)quinone (13). Evidence indicates that 12 and 13 form from free radical reactions involving 10 and the 2,5-di-tert-butylphenyl radical. The different photochemistry of 1 and 2 is discussed in terms of differential steric and conformational effects on the nitroso function which also is evident in their ultraviolet spectra.

The initial reaction mechanism and thermal sensitivity of a fluoropolymer-containing energetic molecular system: the coupling effect of interfacial interactions and free radical reactions

CrystEngComm ◽  
2021 ◽  
Vol 23 (16) ◽  
pp. 3006-3014
Author(s):  
Wen Qian
Keyword(s):  
Free Radical ◽  
Coupling Effect ◽  
Molecular System ◽  
Thermal Sensitivity ◽  
Radical Reactions ◽  
Initial Reaction ◽  
Interfacial Interactions ◽  
Free Radical Reactions ◽  
Molecular Systems ◽  
Reactive Molecular Dynamics

A strategy combining classic and reactive molecular dynamics is applied to find the coupling effect of interfacial interactions and free radical reactions during the initial thermal decomposition of fluoropolymer-containing molecular systems.

Further studies on free-radical pathology in the major central nervous system disorders: effect of very high doses of methylprednisolone on the functional outcome, morphology, and chemistry of experimental spinal cord impact injury

1982 ◽  
Vol 60 (11) ◽  
pp. 1415-1424 ◽  
Author(s):  
H. B. Demopoulos ◽  
E. S. Flamm ◽  
M. L. Seligman ◽  
D. D. Pietronigro ◽  
J. Tomasula ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Central Nervous System ◽  
Nervous System ◽  
Free Radical ◽  
Tissue Injury ◽  
Functional Restoration ◽  
Radical Reactions ◽  
Free Radical Reactions ◽  
Cord Injury

The hypothesis that pathologic free-radical reactions are initiated and catalyzed in the major central nervous system (CNS) disorders has been further supported by the current acute spinal cord injury work that has demonstrated the appearance of specific, cholesterol free-radical oxidation products. The significance of these products is suggested by the fact that: (i) they increase with time after injury; (ii) their production is curtailed with a steroidal antioxidant; (iii) high antioxidant doses of the steroidal antioxidant which curtail the development of free-radical product prevent tissue degeneration and permit functional restoration. The role of pathologic free-radical reactions is also inferred from the loss of ascorbic acid, a principal CNS antioxidant, and of extractable cholesterol. These losses are also prevented by the steroidal antioxidant. This model system is among others in the CNS which offer distinctive opportunities to study, in vivo, the onset and progression of membrane damaging free-radical reactions within well-defined parameters of time, extent of tissue injury, correlation with changes in membrane enzymes, and correlation with readily measurable in vivo functions.

Solvent Effects on the Oxidative Free Radical Reactions of 2-Amino-1,4-naphthoquinones.

ChemInform ◽  
2005 ◽  
Vol 36 (14) ◽  
Author(s):  
Chao-Ming Tseng ◽  
Yi-Lung Wu ◽  
Che-Ping Chuang
Keyword(s):  
Free Radical ◽  
Solvent Effects ◽  
Radical Reactions ◽  
Free Radical Reactions

Simulation of dioxygen free radical reactions

1993 ◽  
Vol 21 (3) ◽  
pp. 256S-256S ◽  
Author(s):  
PEDRO MONIZ-BARRETO ◽  
DAVID A. FELL
Keyword(s):  
Free Radical ◽  
Radical Reactions ◽  
Free Radical Reactions
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